The present invention relates to a rotary laser beam emitting apparatus and, more particularly, to a rotary laser beam emitting apparatus capable of being inclined in a direction coinciding with the direction of a reflector.
A conventional rotary laser beam emitting apparatus for forming a reference plane is used also for finding a target point, for enhancing visibility by go-and-return laser beam scanning and a laser beam point and for forming an inclined reference plane.
A reflector for reflecting a laser beam to find a position is disposed at the target point, the rotary laser beam emitting apparatus emits a laser beam toward the reflector, the reflector reflects the laser beam toward the rotary laser beam emitting apparatus, and then the rotary laser beam emitting apparatus finds the position of the reflector from the reflected laser beam.
The construction of the rotary laser beam emitting apparatus will be described with reference to FIG. 10. A laser beam emitted by a light emitting unit 162 is deflected perpendicularly and turned in a plane by a pentagonal prism 18 included in a rotary light beam projecting unit 13. The laser beam is reflected by a reflector 168 disposed at a target point toward the laser beam emitting apparatus. The reflected light beam falls on the pentagonal prism 18 of the rotary laser beam projecting unit 13 and is reflected by a half mirror 103 (or an apertured mirror) toward a photodetecting unit 104. The light emitting unit 162 comprises a light emitting diode 101, a collimator lens 102 and the half mirror 103. The photodetecting unit 104 comprises a condenser lens 110, a second photodetecting device 114 and a reflected light detecting circuit 116. The laser beam received by a reflected light detecting unit 164 is detected by the reflected light detecting circuit 116. A controller 117 calculates the direction of the reflector 168 on the basis of a detection signal provided by the reflected light detecting unit 164 and a signal provided by an ecnoder 105 and indicating an angular position of the rotary laser bean projecting unit 13, and a scanning motor 15 is controlled by a scanning drive unit 165 to direct the laser beam toward the reflector.
When forming an inclined plane in the direction of the reflector 168, the direction of the reflector 168 and the direction of the rotary laser beam emitting apparatus are calculated on the basis of a detection signal provided by the reflected light detecting circuit 116 and a signal provided by the encoder 105, and then the rotary laser beam emitting apparatus is turned so as to make the directions coincide with each other.
However, this conventional laser beam emitting apparatus detects the emitting direction of the laser beam indirectly on the basis of the signal provided by the encoder interlocked with the rotary laser beam projecting unit 13. Therefore, the direction of the laser beam projected by the rotary laser beam projecting unit 13 must accurately coincide with the output of the encoder.
However, since moving parts have some play, and the moving parts need some play. Accordingly, if the rotary laser beam projecting unit 13 has play in a horizontal direction, the rotary laser beam projecting unit 13 moves as shown in FIG. 11 and the laser beam is translated by a distance A. If the rotary laser beam projecting unit 13 is inclined, the pentagonal prism 18 is inclined as shown in FIG. 12 and the rotating direction changes by an angle B. The distance A and the angle B cause errors in the signal provided by the encoder and an actual laser beam projecting direction, and the laser beam projecting direction does not coincide with the signal provided by the encoder.
Generally, since construction works are carried out in the range of several hundreds meters on the basis of a reference plane and an inclined plane defined by the laser beam, even a slight error brings about serious problems.